1. Field of the Invention
The present invention relates to the field of electronic circuitry in the extremely high frequency region, in the range of operating frequencies up to several GHz. It relates in particular to a printed circuit board arrangement according to the precharacterizing clause of claim 1.
In modern communications technology and in other fields which operate using extremely high frequency, electronic circuits are formed on printed circuit boards (PCBs) which have one or more conductor layers on an electrically insulating supporting board, which conductor layers are structured at least in places and form conductor tracks or surfaces which connect electronic components which are fitted and/or soldered to the supporting board to one another and/or to the outside world.
In the case of relatively large appliance units such as base stations for mobile radio technology, a plurality of separate printed circuit boards are accommodated in one appliance and must be electrically connected to one another after or during installation in the appliance. Many of the required connections must in this case be RF-compatible, in order to allow signals to be reliably passed on from one printed circuit board to the other at high operating frequencies in the GHz range. In principle, such retrospective connections can be soldered, but this involves a considerable amount of labour, particularly when a large number of such connections must be made. It is also possible to make the connections by short lines with plug connectors, although this is likewise associated with considerable labour and in addition occupies a not insignificant space.
2. Discussion of Related Art
If the printed circuit boards to be connected are arranged one above the other or at least partially overlapping, pressure-contact, preferably coaxial RF connections can be used, for example as disclosed in the documents U.S. Pat. No. 6,231,352, U.S. Pat. No. 7,416,418, U.S. Pat. No. 7,210,941, EP-A2-1 289 076 or WO A1 2007/009549.
However, a different situation results with printed circuit board arrangements as shown in FIG. 1 or FIG. 2. In the case of the printed circuit board arrangement 10 shown in FIG. 1, two printed circuit boards 11 and 12 are arranged alongside one another on a common, relatively thick base plate 13 which is used in particular for heat dissipation and, for example, may be composed of aluminium. The two printed circuit boards 11 and 12 are aligned with two opposite edges parallel to one another, and separated, thus forming an intermediate space 14 between them, which must be bridged by RF-compatible electrical connections 15, which are represented schematically by double-headed arrows in FIG. 1. The intermediate space 14 is not absolutely essential, and instead the edges of the printed circuit boards 11, 12 can also directly abut on one another.
In the printed circuit board arrangement 20 shown in FIG. 2, the situation is similar, with the difference that one of the printed circuit boards, specifically the printed circuit board 12′, is designed specifically for a high-power circuit and is therefore additionally provided on the lower face with a dissipation plate 16 which is intended to directly absorb and distribute the heat which is created in the components (a so-called “heat spreader plate”), before it is then passed on to the base plate 13′. By way of example, the dissipation plate 16 may be composed of sintered aluminium. This makes the printed circuit board 12′ thicker than the printed circuit board 11. A corresponding thickness stage is provided for compensation in the base plate 13′.
Connection apparatuses which operate by means of pressure have already been proposed for the electrical connection of printed circuit boards arranged alongside one another, in U.S. Pat. No. 6,612,851, but these act on the upper face and lower face of the printed circuit boards and are therefore not suitable for printed circuit boards arranged on a base plate.
Furthermore, U.S. Pat. No. 6,464,510 has disclosed microwave connectors which connect both printed circuit boards on the upper face by means of pressure contacts. However, the connectors must be installed retrospectively and must be screwed to one or both printed circuit boards, which is tedious and susceptible to faults.
Finally, U.S. Pat. No. 3,591,834 discloses a type of plug connector system, in which the opposite side edges of the two printed circuit boards must be introduced from the side, making contact, into an apparatus which is provided for this purpose. This connection technique is also unsuitable for printed circuit boards which rest on a base plate.